Drilling systems are sometimes utilized for the extraction of hydrocarbons from a subterranean earthen formation via a drilling wellbore into the formation. In some applications, drilling systems are located offshore and include a floating vessel disposed at the waterline, with a drillstring extending from the vessel to the subterranean wellbore. The operations of many floating vessels, such as semi-submersible drilling rigs, drill ships, and pipe-laying ships, are impeded by sea swell. Particularly, sea waves impart an up-and-down motion to a vessel, commonly referred to as “heave,” with the period of the waves ranging anywhere from a few seconds up to about 30 seconds or so and the amplitude of the waves ranges from a few centimeters or inches up to about 15 meters (about 50 feet) or more. This up-and-down motion imparted to the vessel from the waves is then correspondingly imparted to any loads or structures attached to the vessel.
In particular, this heave motion of the loads or structures extending from the vessel is often highly undesirable, and even dangerous, to equipment and personnel. Heave compensation is directed to reducing the effect of this up-and-down motion on a load attached to the vessel. In particular, “passive” heave compensation systems are typically used by fixing the load to a point, such as the sea bed. Sea swell may then cause the vessel to move relative to the load, in which a passive compensator uses compressed air to provide a low frequency damping effect between the load and the vessel. Further, “active” heave compensation systems may be used that typically involve measuring the movement of the vessel using a measuring device, such as a motion reference unit (“MRU”), and using a signal from the MRU that represents the motion of the vessel to compensate for the motion.